1. Field of the Invention
The present invention generally relates to a speaker unit structure, in particular, to a speaker unit with a sound cavity structure having characteristics of being light, thin, flexible, and the like.
2. Description of Related Art
The two most direct sensory systems of human being are visual and audible systems, so for a long time, scientists try their best to develop related elements or system techniques. Recently, electroacoustic speakers are mainly classified into direct and indirect radiating types, and are approximately classified into moving coil, piezoelectric, and electrostatic speakers according to driving manners. The speakers each mainly include an electrode, a vibrating membrane, and a sound cavity in despite of the type thereof.
The electrodes of conventional electric speakers are mostly thin metal plates, and a metal line is connected to an external signal source by tin/lead-soldering the contacts of the electrodes. However, under the trend of fine 3C products and flat family cinemas, flat speakers become popular. Moreover, flexible electronics are tend towards being light, thin, and flexible etc., and in order to enable the flat speaker to have the above characteristics, the structure and the material of the speaker must be considered. A conventional thin metal plate is replaced by a thin electrode fabricated by cladding a conductive layer on a substrate made of high molecular material or paper, such that the whole speaker becomes lighter, thinner, and more flexible. However, in the conventional electrode connection structure of the electrode contact and the metal line, a temperature of the used tin/lead-soldering is up to higher than 180° C., so the electrode having the substrate made of high molecular material or paper may have its substrate deformed or curled due to the heat, or even have the opened contacts. Further, the rigidness of the contact structure of the tin/lead-soldering is too high to be flexible, such that it is impossible to meet the demand of the flexible electronics.
Referring to FIGS. 1A and 1B, a structural cross-sectional view and a schematic top view of a piezoelectric electroacoustic transducer in U.S. Pat. No. 7,141,919 are shown. A piezoelectric sounding body 1 includes a metal plate 2, an insulation layer 3, and a piezoelectric body 4. The piezoelectric sounding body 1 is located on a supporting portion 21 of a case 20, and is spaced from a terminal 22 through a spacing wall portion 24. An insulation material 32 is used for fixing the metal plate 2 on the supporting portion 21, and a conductive adhesive 33 is used for fixing the piezoelectric body 4 on the insulation layer 3, and connecting to the terminal 22.
The piezoelectric electroacoustic transducer enables the vibrating membrane to vibrate by using a piezoelectric material, so as to generate sounds. The connecting position of the conductive adhesive 33 and the terminal 22 may be clearly known from FIG. 1B, the connection between the conductive adhesive 33 and the terminal 22 is a point connection manner, and the structure of the conductive adhesive 33 and the terminal 22 forms a vertical connection. The rigidness of the whole structure is too high to be flexible, such that it is impossible to meet the demand of the flexible electronics.